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JavaScript One Solution

Posted by JASON PETERSEN
JASON PETERSEN
14,266 Points

My for...in loop isn't working. 

const cards = document.getElementsByClassName('card');
for (const card in cards) {
 card.style.backgroundColor = 'skyblue'; 
}

I'm trying to do a for...in loop to iterate through each h2 element, but's not working. I get a TypeError: Cannot set property 'backgroundColor' of undefined.

What did I do wrong??

Thanks!!

Reggie Williams
Reggie Williams
Treehouse Teacher
Reggie Williams
Reggie Williams
Treehouse Teacher

Hey JASON PETERSEN have you tried checking the value of cards with a console.log statement?

JASON PETERSEN
JASON PETERSEN
14,266 Points

Reggie, good idea. When I do that it shows an HTMLCollection. Also when I do a different type of for loop it works correctly. So I did something wrong in my for loop.

2 Answers

jb30
jb30
44,806 Points

Instead of for (const card in cards) {, try for (const card of cards) {. Your current code loops over the properties of cards rather than the iterable objects of cards.

JASON PETERSEN
JASON PETERSEN
14,266 Points

That did it! Thanks!!

I don't know that I understand the difference tho. What's the difference between 'enumerable properties' and 'iterable objects'?

jb30
jb30
44,806 Points

The collection has default properties such as length, and default methods. backgroundColor and other things you set with CSS are also properties. Objects include things like the elements in your collection, or elements of an array.

You could use your for ... in loop to see what it gives you.

for (const p in cards) {
  console.log(p + ": " + cards[p]);
}
Scott Brantley
Scott Brantley
6,084 Points
Scott Brantley
Scott Brantley
6,084 Points

Try removing the 'const' in the loop.

JASON PETERSEN
JASON PETERSEN
14,266 Points

Tried that, no dice.